Got the same error also with an ordinary user on debian Sid (12/10/2013). Remembered I just installed some gtk2 and gtk3 engines. Issue was solved for me by uninstalling gtk3-engines-unico.
-- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org